The present invention relates to a process for treating wastewater streams containing phenolics and more specifically to the extraction of the phenolics with ethers and then the recovery of the phenolics and the recycle of the ethers.
Various methods have been used in the past to remove phenolics (phenol and cresol) from wastewater streams including chemical reaction, adsorption with resins, absorption with macromolecular an substances and liquid-liquid extraction. An example of a chemical reaction method is U.S. Pat. No. 3,843,643, dated Oct. 22, 1974, where a chemical such as hexamethylene tetramine is added to phenolic wastewater so as to react with phenol to form a phenol-hexamethylene tetramine adduct and the adduct is separated from the wastewater with subsequent decomposition of the adduct and further separation of the phenol from the hexamethylene tetramine in which the amine can be recycled either as a solid or concentrated slurry. Other chemical treatment methods for phenolic wastewater involve the use of hydroxides or carbonates of alkali metals in conjunction with chlorine gas (Japanese Patent Application 48-104,352, dated Dec. 27, 1973) or the use of monopersulfuric acid (U.S. Pat. No. 3,711,402, dated April, 1973). However, these chemical reaction methods involve cumbersome recovery and the recycle of solid chemical treating agents or slurries. Also, there may be the costly consumption of the chemical treating agents.
A process where adsorption with resins is used is Japanese Patent Application 4-346,954, dated Dec. 2, 1992, which relates to a process wherein phenols are removed from phenolic wastewater by adsorption onto styrene--divinylbenzene resins, after which the phenols are deadsorbed with a deadsorption agent and recovered. This involves the use of costly adsorption resins and the problem of disposing of them when they are spent.
The absorption technique is illustrated in German Patent Application 2,531,101, dated Jan. 22, 1976, in which phenols are removed from phenolic wastewater by absorption into macromolecular substances, namely poly-alpha-halo-ketones. Once again, this involves the use of costly substances and the attendant disposal problem. Also, with the adsorption and absorption there can be complex regeneration procedures.
Japanese Patent Application 49-080,029, dated Aug. 2,1974, relates to a process wherein phenols are removed from phenolic wastewater using either benzene or toluene as extracting agents with a subsequent distillation to recover either the benzene or toluene and the phenols. It is also known that cumene (isopropylbenzene) can be used commercially for the removal of phenols from phenolic wastewater. However, the extracting agents which have been used have low partition or distribution coefficients making the extraction inefficient.